Process for the preparation of C-substituted pyridines and/or hydrogenated C-substituted pyridines, quinolines and/or hydrogenated quinolines

Abstract

An improved process for the preparation of pyridines and/or hydrogened pyridines that have been substituted with a hydrocarbon group at one or more carbon atoms. gamma -cyanoketone, in a gaseous phase and in the presence of hydrogen, is passed over a first catalyst in a reaction zone to form a reaction mixture containing substituted pyridines and/or hydrogenated pyridines and hydrogen. A hydrogen-containing gas is separated from the reaction mixture and, prior to being recycled, is subjected to a two-step catalytic treatment. In the first catalytic treatment step, the hydrogen-containing gas is passed over an iron, nickel, cobalt, or platinum-containing catalyst at a temperature of between about 250 DEG and 550 DEG C. In the second catalytic treatment step, the hydrogen-containing gas is passed over an iron, nickel, or cobalt catalyst at a temperature of between about 550 DEG and 800 DEG C.

What is claimed is: 
     
       1. In a process for the preparation of pyridines and/or hydrogenated pyridines that have been substituted with a hydrocarbon group at one or more of the carbon atoms, by the steps of: passing a γ-cyanoketone, in a gaseous phase in the presence of hydrogen, over a first catalyst containing a catalytically active component selected from the group consisting of copper, silver, gold, iron, nickel, cobalt, ruthenium, rhodium, palladium, osmium, iridium, platinum and compounds thereof, thereby forming a reaction mixture containing said substituted pyridines and/or hydrogenated pyridines and hydrogen;   separating a hydrogen-containing gas from said reaction mixture; and   subjecting at least a portion of said hydrogen-containing gas to a catalytic treatment and thereafter recycling it to said reaction zone, the improvement comprising carrying out said catalytic treatment in at least two steps wherein,     in said first step, said hydrogen-containing gas to be recycled is passed over a catalyst containing a component selected from the group consisting of iron, nickel, cobalt, platinum, and compounds thereof, at a temperature in the range of between about 250° and 550° C.; and   in said second step, said hydrogen-containing gas to be recycled is passed over a catalyst containing a component selected from the group consisting of iron, nickel, cobalt, and compounds thereof, at a temperature of between about 550° to 800° C.   
     
     
       2. The process of claim 1 wherein the catalyst in both said first and second steps contains nickel. 
     
     
       3. The process of claim 1 or 2 wherein the space velocity of said hydrogen-containing gas in both said first and second steps is in the range of between about 0.25 and 20 N-liters of said gas per gram of catalyst per hour. 
     
     
       4. The process of claim 1 or 2 wherein only a portion of said hydrogen-containing gas separated from said reaction mixture is recycled to said reaction zone. 
     
     
       5. The process of claim 4 wherein additional hydrogen is introduced into said process by adding impure hydrogen to said hydrogen-containing gas to be recycled prior to subjecting said hydrogen-containing gas to said two-step catalytic treatment. 
     
     
       6. The process of claim 1 or 2 wherein said first step is carried out at a temperature of between about 300° and 500° C., and said second step is carried out at a temperature of between about 575° and 700° C.